1. Field of the Invention
This invention relates to electric detonators and, more particularly, to an electric ignition assembly apparatus for the production of electrical explosive detonators having standards of performance and safety, as well as low cost in volume production.
2. Description of the Prior Art
With the development of stringent requirements for performance of explosive devices in both military and commercial applications, a need arose for an apparatus for assembling electrical detonators which would be reliable in operation and which would utilize mechanized production techniques. Thus, the need arose for an assembly apparatus which could produce detonators which were both reliable and reproducible with respect to firing characteristics.
Prior to this invention, no detonator assembly apparatus had been developed which was able to produce reliable and reproducible firing characteristics in the explosive portion of the assembly on a mass production basis. Moreover, such prior apparatus was not able to produce reliable detonator assemblies at reasonable cost.
Prior to this invention, no detonator had been developed which was able to meet reproducible firing requirements on a mass production basis. This was primarily because satisfactory apparatus for assembling such detonators was not available.
Electric detonators of the conventional type are ignition assemblies which comprise a pair of parallel electric conductors extending into the shell from an external firing circuit, a plug of rubber like composition holding the conductors in place and sealing the initiator, a bridge wire connecting the ends of the conductor within the shell, and a heat sensitive ignition composition in contact with the bridge wire. This bridge assembly and installation more than doubles the cost of comparable non-bridge mechanical detonators. For years attempts have been made to construct a low energy electrical detonator with a conductive explosive mixture or pyrotechnic mixture to eliminate the wire bridge. To achieve this many combinations of materials have been tried. The failures that persist are due to the close tolerance that must be maintained between the no fire and the fire requirements. Prior to this invention the assembly process used in the manufacture of conventional detonators comprised the loading of the conductive explosive or pyrotechnic mixture by a predetermined ram pressure technique. Using this technique, an internal electrical resistance measurement is made to determine whether or not the required firing energy would initiate the detonator.
It is accordingly an object of this invention to provide a detonator loading apparatus which permits the pressure ram to be controlled in such a manner as to permit the desired performance of the conductive explosive mixture or pyrotechnic material compressed therein.
It is accordingly another object of this invention to provide an apparatus for manufacturing detonators having ram pressure controlled by the electrical resistance of the conductive explosive or pyrotechnic mixture.
It is also an object of this invention to provide an apparatus for manufacturing detonators having a ram travel control with mechanisms for recycling or rejecting insufficiently loaded detonator housings and a mechanism for rejecting overloaded or improperly aligned detonator housings.
Further objects and the entire scope of the invention will become more fully apparent in the following detailed description and in the appended claims.